My beers always seem to turn out too bitter, but my hop rates are never high. I do notice however that when I try the beer after it has sat for 6 months or more, my chill haze is greatly reduced and the bitterness has drastically changed as well. I know that beers mellow after time but I suspect that somehow some of my bitterness is related to the suspended proteins that cause chill haze. Is this true?

Using certain grains or extracts can cause chill haze but personally I have never experienced bitterness from protien, it could be bad mash efficiency if you are mashing (you would notice with a specific gravity reading) or maybe hops are not being removed before primary ferment.

Hello there.... do you mash yourself (I guess you do ?) It might be good to have a look how you mash and sparge, if you get the temp too high maybe you flush out some tannins from the grains ?
I have heard that can give you a bitterness that will subside after some months.
Cheers James